Influence of Heat Treatment on Structure and Durometric Properties of Coatings Obtained by Surfacing with CSR-04СR27NI7MO3CU2Т Cast Rods

The effect of heat treatment modes on the structure and durometric properties of coatings obtained by surfacing with CSR-04СR27NI7MO3CU2Т cast rods, is considered. It is found that the temperature of 800°С and soaking time of 5 hours are optimal to increase the deposited metal hardness. It is shown that such a phenomenon results from the formation of the austenitic structure hardened by the precipitates of the σ-phase (FeCr), chromium carbides (Cr3C2) and titanium carbides (TiC). The heat treatment modes proposed can be applied in the wear-resistant surfacing technology of chemical equipment parts.

Surface Electric Arc Hardening of Low-Carbon Steels

Examined geometric characteristics, microhardness and features of structure formation in the heat affected zone of steels 09G2, 20L, 20FL. These studies were carried out after surface quenching by a magnetically controlled (scanning) DC electric arc in a protective argon atmosphere. It is shown that electric arc hardening forms on the treated surface of the steel a thin layer of martensitic-austenitic structure with varying composition and hardness. A ferrite-austenitic structure is formed in the region of transition from the base metal to the heat-strengthened metal. This structure contains crushed ferrite grain and winding boundaries between the structural components. On the periphery of austenitic grains martensitic layer is observed. Repeated heating, occurring during heat treatment of the adjacent surface area, is accompanied by a partial decay of martensite and austenite of a pre-hardened structure with the formation of bainite-and sorbitol-like tempering structures. On the surface, experienced repeated heating, the volume fraction of austenite increases. The dependences allowing to control the structural state and depth of the hardening zone are established.

A Comparison of Strengthening Mechanisms of Austenitic Fe-13Mn-1.3C Steel in Warm and Cold High-Pressure Torsion

A study on the role of deformation temperature on a twin-assisted refinement of austenitic structure and phase transformations in high-pressure torsion of high-Mn Hadfield steel single crystals (Fe-13Mn-1.3C, in mass. %) has been carried out. In high pressure-torsion, twinning has been experimentally confirmed as a high-temperature deformation mechanism and has been observed at the temperature 400 °C. An increase in deformation temperature of up to 400 °C decreases the activity of mechanical twinning but does not fully suppress it. A dense net of twin boundaries, which has been produced in cold deformation by high-pressure torsion at room temperature, possesses high thermal stability and stays untransformed after post-deformation annealing at a temperature of 400 °C. In high-pressure torsion at a temperature of 400 °C, the complex effect of high temperature and severe plastic deformation on the strengthening of high-carbon Fe-13Mn-1.3C steel has been observed. A synergetic effect of severe plastic deformation and elevated temperature stimulates a nucleation of nanoscale precipitates (carbides and ferrite) along with deformation-induced defects in austenitic structure. These fine precipitates are homogeneously distributed in the bulk of the material and assist high values of microhardness in high-pressure torsion-processed specimens, which is similar to twin-assisted microstructure.

Influence of the energy electron beam exposure regimes on the structure and mechanical properties of composite coatings

The effect of heat treatment on the structure and properties of composite coatings based on chromium carbide with titanium carbide fabricated by non-vacuum electron beam cladding without has been studied. It was shown that tempering leads to a decrease in microhardness and wear resistance, which is associated with the decomposition of the austenitic structure with the formation of a soft ferrite-carbide structure. The post heat treatment tempering was showed to decrease of microhardness and wear resistance, which leads to the decomposition of the austenitic structure with the formation of a soft ferrite-carbide structure. The bulk quenching of coatings after tempering leads to an increase in microhardness comparable to the values of microhardness in the initial state after electron beam cladding, due to the formation of high hard martensite. The wear resistance of composite coatings after tempering is lower than after cladding due to brittle martensite, which is not able to hold solid carbide particles. The composite coatings obtained at the optimal processing conditions have a combination of improved properties and do not require additional heat treatment, resulting in structural changes, causing a decrease in mechanical properties.

Corrosion Resistance Methods for Stainless Steel

304 grade stainless steel is known to be important in most structural applications due to its high mechanical strength, hardness, and machinability. It is considered a versatile steel that has good formability, can be welded as it is, and is non-magnetic austenitic structure. The corrosion resistance is also excellent at room temperature for most corrosive acids and alkalis. However, its corrosion resistance decreases at higher temperatures when exposed to water for prolonged periods of time. It is sensitive to pitting, crevice and stress corrosion cracking at elevated temperatures. In some cases, the resistance is improved by addition of corrosion inhibitor that negatively affects its formability and welding advantages. Therefore, other methods of corrosion protection are desired. This chapter provides in-depth review of corrosion protections materials and methods that have been used for protecting 304SS in different specific applications. It also provides systemic analysis of the potentiodynamic polarization method to compare the corrosion potential of different materials.

Analysis of 1.4571 Chrome-Nickel Steel Properties after Cold Forming by Bending

The paper deals with the problems of austenitic chrome-nickel steels and their behavior in plastic deformation processes. These steels cannot be hardened by thermal processes due to a stable austenitic structure, therefore the increase of strength is achieved only by cold forming. The deformation mechanisms of the slip or twinning are activated by the effect of the forming force in the steel. Mainly, there is formed deformation-induced martensite whose structure is different from the martensite created by the heat treatment. As the intensive hardening of austenitic chrome-nickel steels under the effect of plastic deformation is beneficial, it adversely affects the machining of these materials.

Effect of plastic deformation rate at room temperature on structure and mechanical properties of high-Mn austenitic Mn-Al-Si 25-3-3 type steel

Purpose: The aim of the paper is to determine influence of plastic deformation rate at room temperature on structure and mechanical properties of high-Mn austenitic Mn-Al-Si 25-3-3 type steel tested at room temperature. Design/methodology/approach: Mechanical properties of tested steel was determined using Zwick Z100 static testing machine for testing with the deformation speed equal 0.008 s-1, and RSO rotary hammer for testing with deformation speeds of 250, 500 and 1000s-1. The microstructure evolution samples tested in static and dynamic conditions was determined in metallographic investigations using light microscopy as well as X-ray diffraction. Findings: Based on X-ray phase analysis results, together with observation using metallographic microscope, it was concluded, that the investigated high-Mn X13MnAlSiNbTi25-3-3 steel demonstrates austenitic structure with numerous mechanical twins, what agrees with TWIP effect. It was demonstrated, that raise of plastic deformation rate produces higher tensile strength UTS and higher conventional yield point YS0.2. The UTS strength values for deformation rate 250, 500 and 1000 s-1 grew by: 35, 24 and 31%, appropriately, whereas in case of YS0.2 these were: 7, 74 and 130%, accordingly, in respect to the results for the investigated steel deformed under static conditions, where UTS and YS0.2 values are 1050 MPa and 700 MPa. Opposite tendency was observed for experimentally measured uniform and total relative elongation. Homogeneous austenitic structure was confirmed by X-ray diffractometer tests. Research limitations/implications: To fully describe influence of strain rates on structure and mechanical properties, further investigations specially with using transmission electron microscope are required. Practical implications: Knowledge about obtained microstructures and mechanical properties results of tested X13MnAlSiNbTi25-3-3 steel under static and dynamic conditions can be useful for the appropriate use of this type of engineering material in machines and equipment susceptible to static or dynamic loads. Originality/value: The influence of plastic deformation at room temperature under static and dynamic conditions of new-developed high-manganese austenitic X13MnAlSiNbTi25-3-3 steels were investigated.